JSON.parse improvement. Call "LookupSymbol" rather than "NewString"...

src/parser.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 4066 matching lines @@
   if (scanner_.is_literal_ascii()) {
     return isolate()->factory()->NewStringFromAscii(
         scanner_.literal_ascii_string());
   } else {
     return isolate()->factory()->NewStringFromTwoByte(
         scanner_.literal_uc16_string());
   }
 }
 
 
+Handle<String> JsonParser::GetSymbol() {
+  int literal_length = scanner_.literal_length();
+  if (literal_length == 0) {
+    return isolate()->factory()->empty_string();
+  }
+  if (scanner_.is_literal_ascii()) {
+    return isolate()->factory()->LookupAsciiSymbol(
+        scanner_.literal_ascii_string());
+  } else {
+    return isolate()->factory()->LookupTwoByteSymbol(
+        scanner_.literal_uc16_string());
+  }
+}
+
+
 // Parse any JSON value.
 Handle<Object> JsonParser::ParseJsonValue() {
   Token::Value token = scanner_.Next();
   switch (token) {
     case Token::STRING:
       return GetString();
     case Token::NUMBER:
       return isolate()->factory()->NewNumber(scanner_.number());
     case Token::FALSE_LITERAL:
       return isolate()->factory()->false_value();
@@ skipping 21 matching lines @@
     scanner_.Next();
   } else {
     if (StackLimitCheck(isolate()).HasOverflowed()) {
       stack_overflow_ = true;
       return Handle<Object>::null();
     }
     do {
       if (scanner_.Next() != Token::STRING) {
         return ReportUnexpectedToken();
       }
-      Handle<String> key = GetString();
+      Handle<String> key = GetSymbol();
       if (scanner_.Next() != Token::COLON) {
         return ReportUnexpectedToken();
       }
       Handle<Object> value = ParseJsonValue();
       if (value.is_null()) return Handle<Object>::null();
       uint32_t index;
       if (key->AsArrayIndex(&index)) {
         SetOwnElement(json_object, index, value, kNonStrictMode);
       } else if (key->Equals(isolate()->heap()->Proto_symbol())) {
         // We can't remove the __proto__ accessor since it's hardcoded
@@ skipping 1016 matching lines @@
                                    info->is_global(),
                                    info->StrictMode());
     }
   }
 
   info->SetFunction(result);
   return (result != NULL);
 }
 
 } }  // namespace v8::internal